Process for grinding gears



1970 YUKIYASU NAKAMURA r 3,550,330

PROCESS FOR GRINDING GEARS Filed Dec. 4, 1967 2 Sheets-Sheet l llllumm.

INVENTOR.

1970 YUKlYASU NAKAMURA 3,550,330

PROCESS FOR GRINDING GEARS 2 Sheets-Sheet 2 Filed Dec. 4, 1967 llllll i'llllll llllllllllll INVENTOR.

W Mam tn United States Patent Oifice 3,550,330 Patented Dec. 29, 1970 U.S. c1. 51-287 3 Claims ABSTRACT OF THE DISCLOSURE A process for grinding gears wherein the gear to be ground is rotated by light frictional engagement with a driven shaft and is meshed with a rotating toothed grindstone after which the gear is rigidly held in a chuck and the gear and grindstone are forcibly rotated at a predetermined speed ratio to effect grinding of the gear.

BRIEF SUMMARY OF THE INVENTION This invention relates to the grinding of gears and in particular to the finish grinding of gear stock.

There are known processes for grinding gears in which the gear to be ground by a grindstone having a spiral grinding groove is rotatably supported and the gear and grindstone are brought into mesh while at rest and then the spiral grindstone is rotated to cause the gear to follow it, andthen the gear is forcibly rotated at a predetermined revolution ratio relative to the spiral grinding grindstone. In this process, however, it is unavoidable that the working efficiency is lowered because it is necessary, for each change of gear stock, to stop the spiral grindstone to permit meshing with the gear to be ground.

The present invention has for its object to improve the working efficiency of this kind of gear grinding process and is characterized in that a gear to be ground is rotated by being yieldability supported so as to be changeable freely in its angular phase relative to its axis and the rotating gear is meshed with a grindstone which is being rotated after which the gear is forcibly rotated at a predetermined speed ratio relative to the grindstone to effect grinding of the gear by the grindstone. Another characteristic feature of the invention is that, for facilitating the meshing engagement, the spiral grindstone is provided at the side surface which first engages the gear with a guide member which has a spiral groove in extension with the spiral groove of the grindstone and is made of a softer material than the grindstone. ,1

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of a gear grinding machine according to the present invention;

FIG. 2 is a sectional view of a portion of the machine in FIG. 1;

FIG. 3 is an enlarged sectional view of a part of the portion of FIG. 2;

FIG. 4 is an explanatory diagram showing the relation between a grindstone and a gear to be ground; and

FIG. 5 is a longitudinal sectional view of a grindstone provided with a guide member connected thereto.

DETAILED DESCRIPTION Referring to FIG. 1, numeral 1 denotes a grindstone supporting base attached to a machine frame 2 so as to be slidable therein front and rear and right and left. A spiral grinding grindstone 4 adapted for being rotated by an electric motor 3 is rotatably supported in frame 2. Numeral 4A denotes spiral grinding grooves of grindstone 4. Numeral 5 denotes a supporting base for a gear to be ground. The base 5 is attached to the machine frame 2 in a manner not shown, and there is rotatably provided at the lower portion of the base 5 a driving shaft 9 driven by an electric motor 6 and a gear assembly 7 and 8. There is provided at the center portion of the shaft 9 a driving center 10 fixedly mounted in shaft 9 for rotation therewith. Numeral 11 denotes a supporting center attached to an upper portion of the supporting base 5. A core shaft 12 is supported between these centers 10 and 11 and carries a gear 13 to be ground. Numeral 13A denotes the teeth of the gear 13, and numeral 14 denotes a bearing for the driving shaft 9. At the upper portion of the driving shaft 9, there is secured a partition wall 15 and there is mounted a clamping tube 16 surrounding the wall 15, so as to be axially slidable so that there is formed an oil pressure chamber 18 between a bottom plate 17 of the tube 16 and the partition wall 15. Numeral 19 is an oil charging and discharging passage for the oil chamber 18. Numeral 20 denotes a chuck secured to the top of the driving shaft 9. The chuck 20 has a plurality of resilient segments 21 projecting upwards at the upper portion of the chuck. The segments 21 have outer tapered surfaces 22 which are in light pressing contact with an annular inclined inner surface of the upper end of the clamping tube 16. A spring 23 upwardly acts on the clamping tube 16 to enable the resilient segments 21 to open outwards, and numeral 24 is a pin for preventing rotation of the clamping tube 16 relative to chuck 20. The lower end of the core shaft 12 is formed with a rod portion 12A supported on the driving center 10. When pressure oil is charged into the oil pressure chamber 18, the clamping tube 16 is lowered against the action of the spring 23 for inwardly moving the resilient segments 21 and the rod portion 12A is thereby clamped and the core shaft 12 is coupled for rotation with the driving shaft 9.

The grinding operation is as follows:

The spiral grindstone 4 is driven by the electric motor 3 at a predetermined regular grinding speed. Then, pressure oil is charged through the oil passage 19 to operate the chuck 20 and couple shafts 9 and 12. The electric motor 6 is then driven to rotate the core shaft 12. When the gear 13 rotates at a predetermined speed ratio relative to the grinding stone 4, the chuck 20 is released so that the core shaft 12 and accordingly the gear 13, is driven by the driving center 10 by the frictional engagement therewith. If the grindstone supporting base 1 is then shifted in the direction of arrow A in FIG. 1, that is, in the direction of its axis 25 in FIG. 4, the gear 13 is moved relative to the grindstone 4 in the direction of arrow B, that is, in a direction parallel to the axis 25, so that the teeth 13A are meshed with the spiral grinding grooves 4A of the grindstone. It is usual in this engagement that the angular phase relation of the two are not in coincidence one with another, but due to the fact that the core shaft 12 is supported by the centers 10 and 11 in light frictional engagement, the gear 13 is changeable freely in its angular phase about its axis, whereby the gear 13 may be corrected in its angular phase position when the teeth 13A are initially brought into side surface contact with the grinding grooves 4A, whereby meshing may be effected smoothly without any difficulty. If, thus, there is now obtained the condition that the gear 13 is meshed with the grindstone 4 in the grinding position as shown by chain lines in FIG. 4, the shift movement of the grinding stone 4 is stopped, whereupon the chuck 20 is operated and the gear 13 is forcibly rotated at a predetermined speed ratio relative to the grindstone 4, and at the same time there is provided the known feed required for grinding between the two, whereby the grinding operation is effected and completed.

When the gear 13 is to be shifted in relation to the grindstone 4, it can be considered that the gear 13 is first moved from outside as shown by arrow C in FIG. 4 and then is moved in parallel with the axis 25 after beginning of the meshing. It is usual for rotating the gear and the grindstone at a predetermined speed ratio that the electric motors 3 and 6 are both synchronous motors, but this can be modified so that the two are driven together mechanically by a single common electric motor. -It is not always necessary for starting the core shaft 12 to Operate the chuck 20 as described above, and such starting can be obtained merely by the friction between the center 10 and the core shaft 12. Additionally, the mounting of the core shaft 12 between the centers 10 and 11 can be also carried out under the condition that the center 10 is maintained in its rotation.

According to the present invention, not only can the working efl'iciency be improved because the gear is meshed with the grindstone which is being rotated, but also these can be meshed smoothly without being damaged because the gear is in rotation when they are meshed and is supported so as to be changeable freely in its angular phase position and can be shifted from the side of the grindstone.

FIG. 5 shows a guide member 26 connected to the spiral grindstone 4 at the side surface of grindstone 4 at which meshing begins for making the meshing smoother. Guide member 26 is made of a material softer than the grindstone, such as rubber or synthetic resin, and the guide member is provided at the periphery thereof with teeth 26A defining a spiral groove which is in extension with the spiral grinding groove of the grindstone 4. With such an arrangement, the teeth 13A of the bear mesh with the spiral groove of the soft material of guide member 21 prior to its meshing with the teeth of the grindstone 4. Thereby improper grinding of the teeth 13A at the time 1 4 of initial meshing is prevented and also any damage between teeth 13A and 4A is avoided, thus making the meshing more accurate and smoother.

What is claimed is:

1. In a process for grinding a gear in which a toothed grindstone is meshed with a gear to be ground and the grindstone and gear are forcibly rotated at a predetermined speed ratio, an improvement comprising rotating the gear to be ground through a drive containing a frictional coupling to provide a yieldable angular support for the gear, meshing the rotating gear with the teeth of a rotating grindstone by relatively moving the gear and grindstone with respect to the axis of revolution of the grindstone, and thereafter rigidly holding the gear and forcibly rotating the gear and grindstone at a predetermined speed ratio to effect grinding of the gear. I

2. 'An improvement as claimed in claim 1, wherein said gear and grindstone are meshed by relative movement in a direction parallel to the axis of revolution of the grindstone.

3. An' improvement as claimed in claim 1, wherein said gear is rotated about an axis which is perpendicular to the axis of revolution of the grindstone.

References Cited UNITED STATES PATENTS 2,385,650 9/l945 Rickenmann 51-71 LESTER M. SWINGLE, Primary Examiner US. Cl. X.R. 5195 

